Abstract: Steel plate for automobile bodies and a method for manufacturing the steel plate are disclosed, the steel plate containing 0.02.about.0.03% of P as an alloying element with a total amount of Cu, Ni, Cr, and Mo being more than 0. 01% but less than 0.08 weight % and being electroplated with a Zn alloy.

Abstract: Steel plate for automobile bodies and a method for manufacturing the steel plate are disclosed, the steel plate containing 0.02.about.0.03% of P as an alloying element with a total amount of Cu, Ni, Cr, and Mo being more than 0.01% but less than 0.08 weight % and being electroplated with a Zn alloy.

Abstract: A corrosion resistant duplex plated sheet steel is disclosed, which comprises a sheet steel having on at least one surface thereof a lower layer of Zn base alloy plating and an upper layer thereon selected from a zinc plating having a coating weight of 0.1-5 g/m.sup.2 and a zinc alloy or zinc composite plating having a coating weight of 0.1-10 g/m.sup.2. The ratio of the coating weight of the lower layer to that of the upper layer is at least 1:1 and in the case of upper layer of zinc alloy or zinc composite plating, it comprises, on a weight basis as metal, at least 80% Zn, and one or more additives as Zn corrosion inhibitors selected from Ni, Co, Mn, Sn, Ti, Al, Mg and Si. The duplex plated sheet steel is suitable for coating thereon with an electrophoretic coating composition and exhibits excellent cratering resistance in cathodic electrophoretic coating and excellent cosmetic resistance after painting.

Abstract: A steel sheet with two or more coatings and a method of producing the same are disclosed. The steel sheet has on at least one side a discontinuous surface layer of an Fe or Fe--Zn base alloy, preferably an Fe--Zn base alloy electrodeposit containing Sn in an amount of 0.01 to 50 mg/m.sup.2, usually in an amount of 1.0 to 50 mg/m.sup.2, preferably in an amount of 3.0 to 30 mg/m.sup.2, and also 5 to 50% by weight of Zn in case Fe--Zn alloy is used, and a layer of Zn--Ni or Zn--Fe alloy electrodeposit, which lies directly under said discontinuous surface layer.

Abstract: A method of plating steel strip with a zinc-nickel alloy in an acidic bath, comprises continuously passing the steel strip through the electrolytic plating bath under the conditions that the concentration of Ni.sup.2+ is kept at a level of 20 g/l or more and the concentration of Zn.sup.2+ at a level of 10 g/l or more and the molar ratio of Ni.sup.2+ /Zn.sup.2+ is restricted to a range of from 1.5 to 4.0 with the speed of passage of the steel strip through the electrolyte relative to the counter-current flow of the electrolyte kept at 10-200 m/min.

Abstract: A steel strip is electrolytically plated with a Zn-Ni alloy in an electrolyte both containing Zn.sup.2+ and Ni.sup.2+ ions together with a strontium compound in an amount of 0.05-10 g/l, calculated as SrSO.sub.4 is disclosed.